In the International patent application WO98/31674 phthalazinone compounds are described as PDE4 inhibitors. In the International patent applications WO02/064584, WO02/085906, WO2004/017974, WO2004/018449, WO2004/018451, WO2004/018457, WO2005/075456 and WO2005/075457 phthalazinone- or pyridazinone-compounds with a piperidinyl substituent are described as PDE4 inhibitors. In the European patent application EP0126651 2,4-dihydro-5-[(substituted) phenyl]-4,4-disubstituted-3H-pyrazol-3-ones and 2,4-dihydro-5-[(substituted) phenyl]-4,4-disubstituted-3H-pyrazol-3-thiones are disclosed for use as cardiotonic and antihypertensive agents. In U.S. Pat. No. 2,903,460 pyrazolone compounds with a piperidinyl substituent are described as analgetic and antipyretic compounds. In the International patent application WO2008138939 pyrazolone compounds with a piperidinyl substituent are described as PDE4 inhibitors. In the International patent application WO2008156102 compounds having a pyrazolone core structure attached to a fused heterocyclic ring system are described as PDE3/4 inhibitors.